Flat heat pipe

ABSTRACT

An exemplary flat heat pipe includes a cover, a wick structure adhered to part of an inner surface of the cover and working medium contained in the wick structure. The cover defines a receiving chamber therein. The wick structure is received in the receiving chamber and includes an interface surface away from the inner surface of the cover. The interface of the wick structure and the exposed inner surface of the cover cooperatively define a vapor passage therebetween. Vaporized working medium enters the vapor passage only from the interface

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to heat transfer apparatuses and, more particularly, to a flat heat pipe with enhanced heat dissipation efficiency.

2. Description of Related Art

Generally, flat heat pipes can efficiently dissipate heat from heat-generating components such as central processing units (CPU). A conventional flat heat pipe includes a hollow cover, a continuous wick structure mounted on an inner surface of the cover and a working medium contained in the wick structure. A vapor chamber is defined between an inner surface of the wick structure. When the cover absorbs heat generated from the heat-generating components, the working medium is vaporized by the heat and enters into the vapor chamber in all directions of the inner surface of the wick structure. Therefore, the vaporized working medium from different directions of the wick structure tends to interfere with each other and forms turbulence. Thus, heat dissipation efficiency and stability performance of the flat heat pipe are badly affected.

What is needed is a flat heat pipe which can overcome the problem of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, isometric view of a flat heat pipe in accordance with a first embodiment of the disclosure.

FIG. 2 is a schematic, longitudinal cross-section view of the flat heat pipe of FIG. 1, taken along line II-II thereof.

FIG. 3 is a schematic, transverse cross-section view of the flat heat pipe of FIG. 1, taken along line III-III thereof.

FIG. 4 is a schematic, longitudinal cross-section view of the flat heat pipe of a second embodiment.

FIG. 5 is a schematic, transverse cross-section view of the flat heat pipe of the second embodiment.

FIG. 6 is a schematic, longitudinal cross-section view of the flat heat pipe of a third embodiment.

FIG. 7 is a schematic, transverse cross-section view of the flat heat pipe of the third embodiment.

FIG. 8 is a schematic, longitudinal cross-section view of the flat heat pipe of a fourth embodiment.

FIG. 9 is a schematic, transverse cross-section view of the flat heat pipe of the fourth embodiment.

FIG. 10 is a schematic, longitudinal cross-section view of the flat heat pipe of a fifth embodiment.

FIG. 11 is a schematic, transverse cross-section view of the flat heat pipe of the fifth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-3, a flat heat pipe 1 in accordance with a first embodiment of the disclosure includes a hollow cover 10, a wick structure 30 mounted on an inner surface of the cover 10, and working medium (not shown) contained in the wick structure 30. The flat heat pipe 1 is used to contact heat-generating components (not shown) to absorb heat generated therefrom.

The cover 10 is integrally formed by one piece of metal such as copper or brass. The cover 10 includes an elongated front plate 11, an elongated rear plate 13 spaced from and facing the front plate 11 and two convex connecting plates 15 located at lateral sides of the flat heat pipe 1 and interconnecting lateral edges of the front plate 11 and the rear plate 13. Opposite ends of the front plate 11 and the rear plate 13 are pressed toward each other and sealed to form a first end 17 and a second end 19. Inner surface of the front plate 11, the rear plate 13 and the connecting plates 15 cooperatively define a receiving chamber 16 therebetween. One end of the flat heat pipe 1 approaching the first end 17 is an evaporating portion to absorb heat generating from the heat-generating components. The other end approaching the second end 19 is a condensing portion to condense vaporized working medium.

The wick structure 50 is a screen made of wires mesh or a sintered body sintered by metal powder. The wick structure 50 has a substantially form of triangular pyramid, adhered to inner surfaces of the first end 17 and one of the connecting plate 15. The wick structure 50 slantwise extends towards the second end 19 along a longitudinal direction of the cover 10. A volume of the wick structure 30 is equal to a half of a cubage of the receiving chamber 16.

A volume of the wick structure 30 decreases from an end contacting the first end 17 of the cover 10 to the other end contacting the second end 19 of the cover 10. A transverse cross section of the end contacting the first end 17 is oval. The wick structure 30 has a lateral surface 31, two side surfaces 33, an arc-shaped connecting surface 35 and an interface 37. The lateral surface 31 is adhered to and overspreads the inner surface of the first end 17. The side surfaces 33 extend from opposite edges of the lateral surface 31 and are adhered to part of the inner surfaces of the front plate 11 and the rear plate 13, respectively. A surface area of each side surface 33 is equal to a half of that of the inner surface of the front plate 11 or the rear plate 13. A width of each side surface 33 decreases from the first end 17 to the second end 19.

The connecting surface 35 extends from a top edge of the lateral surface 31 and is adhered to whole of the inner surface of the top connecting plate 15 along the longitudinal direction of the cover 10. The interface 37 extends from another edge of the lateral surface 31 and connects ends of the side surfaces 33 near to the bottom connecting plate 15. The interface 37, the connecting surface 35, and the side surfaces 33 intersect the topmost edge of the second end 19. The interface 37 is elongated and is away from the inner surface of the second end 19 and the bottom connecting plate 15. The interface 37, an inner surface of the bottom connecting plate 15 away from the connecting surface 35, and the exposed inner surfaces of the front plate 11 and the rear plates 13 cooperatively define a vapor passage 18 therebetween. A volume of the wick structure 30 is equal to a cubage of the vapor passage 18.

When the evaporating portion of the flat heat pipe 1 absorbs heat generated from the heat-generating components, the absorbed heat makes the working medium in the wick structure 30 be vaporized and enter into the vapor passage 18 only from the interface 37 of the wick structure 30. So the vaporized working medium enters into the vapor passage 18 in a smaller angle range relative to the conventional flat heat pipe. Thus, interference between the vaporized working medium in the vapor passage 18 is decreased relative to the conventional flat heat pipe. A probability of forming turbulence of the vaporized working medium is decreased.

Following table shows heat transfer performance of the flat heat pipe 1 via adjusting a volume proportion of the vapor passage 18 to the receiving chamber 16.

Average of the max load Average of thermal Proportion Number of heat transfer (W) resistance (° C./W) 0.45 30 31.5 0.45 0.5 30 32 0.2 0.67 30 31 0.15 0.7 30 25 0.13 Remarks: 1: A length of the flat heat pipe is 160 mm, before pressed, a height of the heat pipe is 6 mm, and after pressed, a height of the flat heat pipe is 1.5 mm. 2: The working temperature is 50 Celsius degrees. 3: A number of the tested flat heat pipes is 30.

It can be concluded from the above table, the flat heat pipe 1 has a smaller liquid resistance and greater capillary force when the cubage of the vapor passage 18 is equal to a half of that of the receiving chamber 16.

Referring to FIGS. 4-5, a flat heat pipe 1 a of a second embodiment is shown. The flat heat pipe 1 a is similar to the flat heat pipe 1 of the first embodiment, except that the flat heat pipe 1 a has a wick structure 30 a different from the wick structure 30. The wick structure 30 a has a substantially triangular prism and includes a lateral surface 31 a, a first connecting surface 35 a, a second connecting surface 36 a, two side surfaces 33 a, and an interface 37 a. The lateral surface 31 a is adhered to and overspreads the inner surface of the first end 17. The first connecting surface 35 a and the second connecting surface 36 a extend from top and bottom edges of the lateral surface 31 a and are respectively adhered to part of the inner surfaces of the connecting plates 15. The first connecting surface 35 a and the second connecting surface 36 a respectively cover right parts of the inner surfaces of the connecting plates 15 along the longitudinal direction of the cover 10. The second connecting surface 36 a is longer than the first connecting surface 35 a along the longitudinal direction of the cover 10. The side surfaces 33 a extend opposite edges of the lateral surface 31 a and are respectively adhered to part of the inner surfaces of the front plate 11 and the rear plate 13. The interface 37 a connects the side surfaces 33 a, the first connecting surface 35 a and the second connecting surface 36 a. The interface 37 a, the side surfaces 33 a, the first connecting surface 35 a and the second connecting surface 36 a intersect a line 34 a away from and at a right side of the topmost edge of the inner surface of the second end 19. The interface 37 a, the exposed inner surfaces of the connecting plates 15, the front plate 11 and the rear plate 13 cooperatively define a vapor passage 18 a therebetween.

Referring to FIGS. 6-7, a flat heat pipe 1 b of a third embodiment is shown. The flat heat pipe 1 b is similar to the flat heat pipe 1 of the first embodiment, except that the flat heat pipe 1 b has a wick structure 30 b different from the wick structure 30. In this embodiment, the wick structure 30 b has a substantially form of triangular pyramid and is adhered to and overspreads the inner surfaces of the top connecting plate 15 and the front plate 11. The wick structure 30 b slantwise extends from the first end 17 to the second end 19 along the longitudinal direction of the cover 10. The wick structure 30 b is spaced from the bottom connecting plate 15 and the rear plate 13. An interface 37 b of the wick structure 30 b is formed at a bottom end of the wick structure 30 b oriented towards the bottom connecting plate 15 and the rear plate 13. The interface 37 a, the inner surfaces of the bottom connecting plate 15 and the rear plate 13 cooperatively define a vapor passage 18 b therebetween.

Referring to FIGS. 8-9, a flat heat pipe 1 c of a fourth embodiment is shown. The flat heat pipe 1 c is similar to the flat heat pipe 1 of the first embodiment, except that the flat heat pipe 1 c has a wick structure 30 c different from the wick structure 30. In this embodiment, the wick structure 30 c has a substantially form of cube and is adhered to and overspreads the inner surface of the top connecting plate 15. The wick structure 30 c evenly extends towards the bottom connecting plate 15 along a transverse direction of the cover 10 until fills of a top half of the receiving chamber 16. The wick structure 30 c evenly extends from the first end 17 to the second end 19 along the longitudinal direction of the cover 10. An interface 37 c is formed on a bottom ends of the wick structure 30 c facing the bottom connecting plate 15. The interface 37 c, the inner surface of the bottom connecting plate 35 c, and the exposed inner surface of the front plate 11 and rear plate 13 cooperatively define a vapor passage 18 c therebetween.

Referring to FIGS. 10-11, a flat heat pipe 1 d of a fifth embodiment is shown. The flat heat pipe 1 d is similar to the flat heat pipe 1 of the first embodiment, except that the flat heat pipe 1 d has a wick structure 30 d different from the wick structure 30. In this embodiment, the wick structure 30 d is substantially cubical and arranged on a central of the cover 10 along the longitudinal direction of the cover 10 to divide the receiving chamber 16 into three parts. Two vapor passages 18 d are defined between the connecting plates 15 and top and bottom ends of the wick structure 30 d. Lateral surfaces 31 e, 31 d of the wick structure 30 d are respectively adhered to a central portion of the inner surface of the first end 17 and the second end 19. Side surfaces 33 d connect the lateral surfaces 31 e, 31 d and are respectively adhered to central portions of the front plate 11 and the rear plate 13. The wick structure 30 d evenly extends from the first end 17 to the second end 19 along the longitudinal direction of the cover 10.

It is believed that the disclosed embodiment(s) and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure. 

What is claimed is:
 1. A flat heat pipe comprising: a hollow cover defining a receiving chamber therein; a wick structure received in the receiving chamber and adhered to a part of an inner surface of the cover, the wick structure comprising an interface surface away from the inner surface of the cover; and working medium contained in the wick structure; wherein the interface of the wick structure and the exposed inner surface of the cover cooperatively define a vapor passage therebetween, and vaporized working medium enters the vapor passage only from the interface.
 2. The flat heat pipe as in claim 1, wherein a volume of the wick structure is equal to a cubage of the vapor passage.
 3. The flat heat pipe as in claim 1, wherein the cover comprises an elongated front plate, an elongated rear plate spaced from and facing the front plate and two connecting plates interconnecting lateral edges of the front plate and the rear plate, inner surfaces of the front plate, rear plate, and connecting plate cooperatively define the receiving chamber therebetween, and opposite ends of the front plate and the rear plate are pressed toward each other and sealed to form a first end and a second end.
 4. The flat heat pipe as in claim 3, wherein one end of the wick structure is adhered to an inner surface of the first end, and the wick structure slantwise extends towards the second end along a longitudinal direction of the cover from the end thereof.
 5. The flat heat pipe as in claim 4, wherein a volume of the wick structure decreases from the end adhered to the first end to the other end away from the end adhered to the first end.
 6. The flat heat pipe as in claim 5, wherein the wick structure comprises a lateral surface adhered to and overspreads the inner surface of the first end, two side surfaces extending from opposite edges of the lateral surface and adhered to part of the inner surfaces of the front plate and the rear plate, a connecting surface extending from an edge of the lateral surface and adhered to whole of the inner surface of one of the connecting plates along the longitudinal direction of the cover, and the interface extending from another edge of the lateral surface and connecting ends of the side surfaces away from the connecting surface, the interface, the inner surface of the other connecting plate away from the wick structure, and the exposed inner surfaces of the front plate and the rear plates cooperatively define the vapor passage therebetween.
 7. The flat heat pipe as in claim 6, wherein the interface, the connecting surface, and the side surfaces intersect an edge of the second end.
 8. The flat heat pipe as in claim 5, wherein the wick structure comprises a lateral surface adhered to and overspreads the inner surface of the first end, a first connecting surface and a second connecting surface extending from top and bottom edges of the lateral surface and respectively adhered to part of the inner surfaces of the connecting plates, and two side surfaces extending two edges of the lateral surface and adhered to part of the inner surfaces of the front plate and the rear plate, the interface connecting the side surfaces, the first connecting surface and the second connecting surface, and the interface, the exposed inner surfaces of the connecting plates, the front plate and the rear plate cooperatively define the vapor passage therebetween.
 9. The flat heat pipe as in claim 8, wherein the interface, the side surfaces, the first connecting surface and the second connecting surface intersect a line away from the inner surface of the second end.
 10. The flat heat pipe as in claim 8, wherein the second connecting surface is longer than the first connecting surface along the longitudinal direction of the cover.
 11. The flat heat pipe as in claim 3, wherein the wick structure is adhered to and overspreads the inner surfaces of one of the connecting plates and the front plate, slantwise extends from the first end to the second end along the longitudinal direction of the cover, and spaced from the other connecting plate and the rear plate, the interface of the wick structure is formed at a bottom end of the wick structure oriented towards the other connecting plate and the rear plate, and the interface, the inner surfaces of the other connecting plate and the rear plate cooperatively define the vapor passage therebetween
 12. The flat heat pipe as in claim 3, wherein the wick structure is adhered to and overspreads the inner surface of one of the connecting plates, evenly extends towards the other connecting plate along a transverse direction of the cover, and evenly extends from the first end to the second end along a longitudinal direction of the cover.
 13. The flat heat pipe as in claim 12, wherein the wick structure fills a half of the receiving chamber, the interface surface is formed on an end of the wick structure and faces the other connecting plate, the interface and the exposed inner surfaces of the front plate and rear plate cooperatively define the vapor passage therebetween.
 14. The flat heat pipe as in claim 3, wherein the wick structure is arranged on a central of the cover along a longitudinal direction of the cover to divide the receiving chamber into three parts, and two vapor passages are defined between the inner surfaces of the connecting plates and opposite sides of the wick structure.
 15. The flat heat pipe as in claim 14, wherein the wick structure extends from the first end to the second end of the cover and side surfaces thereof are respectively adhered to central portions of the front plate and the rear plate. 